As is calculated with three radiometric spectra, instrument reliability can be best determined by comparing the three separate spectra, before analyzing the remote sensing reflectance. All radiometers and the solar sensor (TriOS, ASD, WISP-3, TACCS, and Microtops) provide spectra which were compared. and spectra from TriOS, ASD, and WISP-3 were compared too. Finally, the end-product from TriOS, ASD, and WISP-3 and from TACCS and ASD were compared. For two stations in Vänern, (from the above-water instruments) had to be compared with (from the below-water instruments). Instead of calculating normalized water-leaving radiances (e.g., 24), the relative difference between and for those stations where TACCS measurements were available was computed with the Hydrolight software. Hydrolight runs were made for Station 1A, which was on August 3, 2011, at 9.45 UTC, using Chl: , SPM: , aCDOM: (as measured in situ), including fluorescence and Raman scatter, assumed specific optical properties and phase function according to the Fournier-Forand phase function with for Chl and for SPM, a wind speed of and optically infinitely deep water. Output reflectance spectra were produced for 350 to 800 nm at 5 nm intervals and interpolated to 1 nm scale. The relative difference between the modelled and was found to be around . This factor was used to convert from TriOS, ASD, and WISP-3 to for comparison with the TACCS and ASD for both stations 1A and 1B (for which the concentrations were very similar while there was just a 2-h difference in time).